The invention relates to a semiconductor device having a semiconductor body which comprises a circuit element with a part formed from doped polycrystalline silicon.
The term semiconductor device includes, for example, diodes, transistors and integrated circuits.
Polycrystalline silicon is silicon in which crystallites can be demonstrated by X-ray analysis. The size of said crystallites is at least approximately 15 .ANG..
The presence of grain limits in polycrystalline silicon means that, electrically, this material is inhomogeneous, while amorphous and monocrystalline silicon -in the absence of grain limits-are homogeneous materials, electrically.
In semiconductor devices, polycrystalline silicon is used for many purposes, for example, as a diffusion source on a semiconductor body, as a conductive material, for example, for gate electrodes in MOS transistors, and as a resistive material.
In all these applications the polycrystalline silicon may comprise a dopant influencing the electric conductivity, which dopant as such determines the electric conductivity in the polycrystalline silicon and/or can be transferred to a semiconductor body.
A problem with polycrystalline silicon is that treatments at elevated temperatures, as are usual upon tempering and diffusion, for example, may give rise to reduced stability and poorer reproducibility of the semiconductor device.
For example, crystal growth easily occurs in polycrystalline silicon when the temperature rises. When the crystal size becomes of the order of magnitude of the thickness of a polycrystalline layer, a substrate on which the layer is present can be undesirably attacked upon etching.